Description

Return Values

If the correct value would cause overflow, a range error occurs and
exp2(), exp2f(), and exp2l() return the value of the macro HUGE_VAL, HUGE_VALF,
and HUGE_VALL, respectively.

If x is NaN, a NaN is returned.

If x is ±0, 1 is returned.

If x is -Inf, +0 is returned.

If x is +Inf, x is returned.

Errors

These functions will fail if:

Range Error

The result overflows.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception will be raised.

Usage

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling
these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is
non-zero, an exception has been raised. An application should either examine the
return value or check the floating point exception flags to detect exceptions.